William L. Headrick,, Alireza Rezaie, William G. Fahrenholtz,
Volume 5, Issue 2 (6-2008)
Abstract
gasification (BBLG). One particularly harsh application is linings for gasifiers used in the
treatment of black liquor (BL). Black liquor is a water solution of the non-cellulose portion of the
wood (mainly lignin) and the spent pulping chemicals (Na2CO3, K2CO3, and Na2S). Development
of new refractory materials for the black liquor gasification (BLG) application is a critical issue
for implementation of this technology. FactSage® thermodynamic software was used to analyze
the phases present in BL smelt and to predict the interaction of BL smelt with different refractory
compounds. The modeling included prediction of the phases formed under the operating
conditions of high temperature black liquor gasification (BLG) process. At the operating
temperature of the BLG, FactSage® predicted that the water would evaporate from the BL and that
the organic portion of BL would combust, leaving a black liquor smelt composed of sodium
carbonate (70-75%), potassium carbonate (2-5%), and sodium sulfide (20-25%). Exposure of
aluminosilicates to this smelt leads to significant corrosion due to formation of expansive phases
with subsequent cracking and spalling. Oxides (ZrO2, CeO2, La2O3, Y2O3, Li2O, MgO and CaO)
were determined to be resistant to black liquor smelt but non-oxides (SiC and Si3N4) would oxidize
and dissolve in the smelt. The other candidates such as MgAl2O4 and BaAl2O4 were resistant to
sodium carbonate but not to potassium carbonate. LiAlO2 was stable with both sodium carbonate
and potassium carbonate. Candidate materials selected on the basis of the thermodynamic
calculations are being tested by sessile drop test for corrosion resistance to molten black liquor
smelt. Sessile drop testing has confirmed the thermodynamic predictions for Al2O3, CeO2, MgO
and CaO. Sessile drop testing showed that the thermodynamic predictions were incorrect for ZrO2.
